Method for manufacturing a drive shaft, bending straightening device and drive shaft

Abstract

Method for manufacturing a drive shaft (1) which has at least two sections (10, 11a, 11b) welded together, at least one of which is designed as a hollow shaft, in which a roll forming process is carried out in the area of ​​the welded joint (14a, 14b) of the welded sections, characterized in that the roll forming process is carried out in a bending straightening device (20, 20'), wherein a straightness measurement of the drive shaft (1) for bending straightening and the roll forming process are carried out in the same setup in the bending straightening device (20, 20').

Description

[0001] The invention relates to a method for manufacturing a drive shaft which has at least two sections welded together, at least one of which is designed as a hollow shaft, in which a rolling action is carried out in the area of ​​the welded joint of the sections welded together.

[0002] Furthermore, the invention relates to a bending straightening device comprising at least one abutment against which a shaft can be supported laterally and rotatably about its longitudinal axis, a drive device for rotating the shaft about its longitudinal axis, means for measuring the straightness of the shaft, and means for straightening the shaft while it is supported on the at least one abutment, according to the preamble of claim 10.

[0003] Furthermore, the invention relates to a drive shaft for a motor vehicle with at least two sections welded together by material bonding, according to the preamble of claim 11.

[0004] In vehicle manufacturing, drive shafts for torque transmission were originally produced as solid shafts. Coupling structures, for example for connecting a constant velocity joint or the like, were formed directly on the solid shaft. To reduce component weight, it is known to design drive shafts as hollow shafts, as described, for example, in DE 21 35 909 A. In DE 21 35 909 A, this hollow shaft is manufactured from a single piece of tubing. This can be done, for example, by rotary swaging. However, this method limits the flexibility of the shaping.

[0005] Furthermore, drive shafts are known to be assembled from several initially separate individual parts. By using welding processes, hollow components can be designed to be more load-specific in order to achieve further weight savings. However, such a joint usually results in a loss of strength, which can be further exacerbated by dissimilar material pairings.

[0006] German patent application DE 10 2012 011 442 A1 describes a multi-part drive shaft for connecting two constant velocity joints. This drive shaft comprises a central section, which is designed as a tube with a constant inner diameter along its entire length and has two axial ends, as well as two wave-shaped journals as end sections, each welded to one of the axial ends of the central section.

[0007] Another drive shaft of this type is disclosed in DE 10 2013 006 792 A1. In this design, at least one groove-shaped recess is created in the shaft's circumference by rolling with a rolling tool in the area of ​​the weld joint. The resulting compressive residual stresses improve its dynamic strength. The strength is to be specifically adjusted by creating the circumferential recess in the outer surface of the shaft within the heat-affected zone of the preceding welding process. In particular, the rolling is intended to increase the compressive residual stresses in the shaft material and thereby achieve the desired work hardening. By introducing compressive residual stresses into the near-surface layer of the heat-affected zone or an area enclosing it, the tensile stress that can be withstood is to be increased, leading to an increase in dynamic strength.The creation of the recess, which is arranged as a depression next to the actual weld seam, can be carried out immediately after the welding process.

[0008] DE 10 2009 012 973 A1 also discloses a metallurgical connection between two cylindrical metal elements, in particular pipe elements, by means of pressure welding or friction welding and with the formation of at least one outer weld bead. This weld bead can be applied to one of the cylindrical elements, for example by rolling, to cover the joint and to serve as sacrificial material with respect to corrosion. A thickening remains at the joint.

[0009] DE 10 2013 008 658 A1 describes a further drive shaft in which a bevel gear is connected to a hollow shaft by friction welding. The resulting weld seam is smoothed by roller burnishing. Roller burnishing introduces compressive stress into the weld seam to prevent crack growth and partial welding of the individual parts. Roller burnishing also leads to an increase in the strength of the weld seam. For example, roller burnishing can also close any gap that may be present after friction welding, thus preventing, for instance, only partial welding of the individual parts.

[0010] A generic drive shaft with the features of the preamble of claim 11 is known from DE 103 06 865 B3.

[0011] Integrating roller burnishing into the manufacturing process proves difficult. Roller burnishing is typically performed using a dedicated fixture. The drive shaft is transported to this fixture, processed there, and then transported from there to any subsequent manufacturing steps. The manufacturing process for the drive shaft is therefore quite complex.

[0012] In connection with cardan shafts, a straightening tool is known from DE 25 56 971 A1, in which straightening is carried out by pressing. Width and diameter variations can also be compensated for by pressing. However, these processes are necessarily linked.

[0013] A bending straightening device of the generic type with the features of the preamble of claim 10 is known, for example, from DE 10 2010 056 616 A1. Further bending straightening devices suitable for drive shafts are known, for example, from DD 294 111 A5, DE 10 2018 006 987 A1 and DE 10 2019 114 112 A1.

[0014] Against this background, the invention is based on the objective of specifying a method for manufacturing a drive shaft in which a rolling process for increasing service life is more efficiently integrated into existing process chains for the production of lightweight, torsionally stressed hollow components, as well as a suitable bending straightening device and a drive shaft.

[0015] This problem is initially solved by a method according to claim 1. This method is characterized in that the roll forming is carried out in a bending straightening device, wherein a straightness measurement of the drive shaft for bending straightening and the roll forming are carried out in the same setup in the bending straightening device.

[0016] By integrating roll forming into the straightening process, the cycle times required for roll forming remain minimal. In particular, it is not necessary to move the drive shaft to a dedicated roll forming unit. Instead, roll forming and straightening can be performed in the same setup of the drive shaft. It should be emphasized that, unlike straightening, in the solution according to the invention both processes, namely roll forming and straightening, remain independent of each other and do not interact. In this respect, the solution according to the invention allows for greater flexibility with regard to component optimization.

[0017] Specific embodiments of the invention are the subject of further patent claims.

[0018] In particular, a rotation of the drive shaft for straightness measurement can be used to detect dimensional deviations in the bending straightening device for the tightening of the weld joint, in order to keep the additional time required for tightening low.

[0019] In a special design variant, straightness measurement can begin during the rolling process itself, with a view to particularly efficient manufacturing.

[0020] Bending straightening is preferably performed in the bending straightening device after roll forming and straightness measurement in the roll forming setup. This process can therefore be very efficiently integrated with the roll forming process.

[0021] According to another special design, the drive shaft can be hardened before rolling. Any distortion caused by hardening is compensated for by bending and straightening.

[0022] Alternatively or additionally, the drive shaft can be tempered after rolling to adjust its strength parameters as desired. If necessary, tempering can be limited to sections of the drive shaft, or sections of the drive shaft can be tempered with different parameters.

[0023] According to another special design, a weld bead of the weld joint can be removed by machining before burnishing. This allows for a particularly homogeneous surface topography in the area of ​​the weld seam, which is then hardened by subsequent burnishing.

[0024] According to another special embodiment, the drive shaft in the bending straightening device can be rotatably supported on a lateral abutment for bending straightening, with a roller or ball for tightening arranged opposite the abutment and pressed laterally against the drive shaft in the direction of the abutment during tightening. This enables particularly short cycle times, as the drive shaft can be clamped very quickly in the bending straightening device. Rotation of the drive shaft can be achieved, for example, by clamping it between two opposing mandrels.

[0025] However, it is also possible to provide a fixed rolling tool on the bending straightening device for the fixed rolling process. This tool encloses the drive shaft in a ring-like manner and also allows the shaft to be rotatably mounted. In this case, rotation of the drive shaft can be achieved, for example, by clamping one end of it in a rotatable chuck or similar device.

[0026] According to another special embodiment, the drive shaft can have a central section in the form of a hollow shaft and end sections connected to its ends, each of which has coupling structures for torque transmission. The relevant welds between the end sections and the central section can be subjected to synchronous roll forming in the bending straightening device, which in turn has a positive effect on the manufacturing time.

[0027] Claim 10 further specifies a bending straightening device suitable for carrying out the method described above. This device comprises at least one abutment against which a shaft can be supported laterally and rotatably about its longitudinal axis, a drive device for rotating the shaft about its longitudinal axis, means for measuring the straightness of the shaft, means for straightening the shaft while it is supported against the at least one abutment, a roller or cylinder arranged opposite the abutment, and a pressure device that pushes the roller or cylinder towards the abutment so that the roller or cylinder can be brought into lateral contact with the shaft for rolling. With such a bending straightening device, for example, a drive shaft can be manufactured very quickly and efficiently, as the rolling of partial sections of the shaft does not require re-clamping.In addition to the reduced handling effort, the need for floor space for suitable manufacturing equipment is also reduced.

[0028] In particular, a drive shaft according to claim 11 for a motor vehicle can be created with at least two sections welded together in a material bond, at least one of which is designed as a hollow shaft, wherein the drive shaft is hardened and tempered at a welded joint between two of the sections welded together in a material bond, has a machined surface and has a rolled surface structure with imprinted compressive residual stresses in a radially outer edge region.

[0029] The following section describes in more detail ways of implementing the invention with reference to exemplary embodiments shown in the drawings. The drawings show: Fig. 1. A flowchart illustrating an exemplary embodiment of a method for manufacturing a drive shaft, Fig. 2 a schematic representation of a bending straightening device with means for both bending straightening and rolling, and in Fig. 3 A schematic representation of another bending straightening device with means for both bending straightening and rolling.

[0030] The embodiments explained in more detail below relate first to the manufacture of a drive shaft 1 which has at least two sections 10, 11a, 11b that are bonded together, in particular welded.

[0031] For illustrative purposes, the drive shaft 1 of the exemplary embodiment has a central section 10 in the form of a hollow shaft and end sections 11a and 11b connected to its ends.

[0032] The end sections 11a and 11b can, for example, be connected to the central section 10 of the drive shaft 1 by welding. Fig. 2 and Fig. 3 The corresponding welded joints are designated with reference numerals 14a and 14b. Friction welding is preferably used as the joining process to generate a metallurgical bond between sections 10, 11a, and 11b without a large heat-affected zone.

[0033] Furthermore, the end sections 11a and 11b can be made of a different material than the central section 10 of the drive shaft 1. In particular, differently alloyed steels can be used for the individual sections 10, 11a and 11b of the drive shaft 1.

[0034] The welded sections 10, 11a, 11b can transition smoothly into one another at the welded joints 14a and 14b with a constant outer cross-section.

[0035] The end sections 11a and 11b each have coupling structures 12a and 12b for torque transmission. These coupling structures 12a and 12b can be designed, for example, as splined shafts, serrated teeth, or the like. They can be formed and / or machined on the respective end section 11a, 11b.

[0036] The end sections 11a and 11b can themselves be designed as hollow shafts. However, it is also possible to manufacture them from solid material. Furthermore, it is possible to provide a solid material structure, at least in the area of ​​the coupling structures 12a and 12b, which can optionally transition into a hollow shaft section 13a, 13b for connection to the central section 10.

[0037] Especially in the Fig. 2 and Fig. The drive shaft 1, shown in more detail below as an example, can be designed, in particular, as a profiled shaft for connecting two constant velocity joints or the like. For this purpose, the coupling structures 12a and 12b can be brought into torque-transmitting engagement with corresponding coupling structures on the respective inner parts of the constant velocity joints.

[0038] However, it should be emphasized that the drive shaft 1 shown in the figures is merely exemplary and can also be designed in other ways. In particular, the number of welded elements of the drive shaft 1 can be smaller or larger than shown. Furthermore, other drivetrain components besides the aforementioned constant velocity joints can be connected via the coupling structures 12a and 12b.

[0039] The welded joints 14a, 14b between the individual sections 10, 11a, 11b of the drive shaft 1 would weaken its strength to a certain extent. This weakening is counteracted here by local roll forming in a region A around the welded joints 14a, 14b. The roll forming process imparts compressive residual stresses to the radially outer edge region of the drive shaft 1 in region A around the welded joints 14a, 14b through plastic deformation, which increases its strength.

[0040] Preferably, area A extends over an axial length of approximately 5 to 50 mm. In particular, the actual weld joint 14a, 14b can also be rolled over. The compressive residual stresses induced by the rolling process can be adjusted so that they are not completely eliminated by subsequent process steps, but rather remain to a desired degree on the finished drive shaft 1.

[0041] An exemplary embodiment of a method for manufacturing such a drive shaft 1 will now be presented using the following examples: Fig. 1 will be explained in more detail.

[0042] The aim here is to further reduce the weight of a torsionally loaded hollow component, preferably also by optionally using a hybrid material combination of differently alloyed steels.

[0043] In Fig. 1. First, the sections of the drive shaft 1 that are later to be joined together by welding are manufactured separately (see a in Fig. 1) In the illustrated embodiment, these are the end sections 11a and 11b, of which in Fig. Figure 1 shows only one example, as well as the central section 10 in the form of a hollow shaft. The manufacturing processes that can be used for this purpose can, in principle, be chosen arbitrarily.

[0044] In the present case, for example, the end sections 11a and 11b are turned into pins and then provided with a toothing for the coupling structures 12a and 12b.

[0045] The central section 10 can, for example, be cut off from a pipe section to a desired length.

[0046] However, these sections 10, 11a, 11b can also be manufactured in other ways, for example by forming technology.

[0047] Subsequently, the sections 10, 11a, 11b required for a drive shaft 1 are assembled and welded together as already mentioned above, for example, but not limited to, friction welding (see b in Fig. 1).

[0048] In a further step (see c in Fig. 1) For example, the final outer contour of the drive shaft 1 can be produced by machining. Any weld beads 15 can be removed in this process, as shown in Fig. 1 is illustrated by turning them down. Remaining weld beads 15 would be disadvantageous both for the processing steps explained below and for the component properties.

[0049] By means of targeted heat treatment (see d in Fig. 1) Preferably following the aforementioned machining process, properties such as hardness, strength, and ductility can be locally adjusted as required. In the area of ​​the welded joints 14a and 14b, a hardened and fine-grained material is thus present.

[0050] During hardening, distortions can occur, i.e., dimensional deviations from a desired target shape, which are induced, for example, by residual stresses from microstructure transformation processes.

[0051] To eliminate dimensional deviations resulting from hardening or other preceding manufacturing steps, the drive shaft 1 is straightened (see f in Fig. 1).

[0052] The process used for this is bend straightening in a suitable bend straightening device. During bend straightening, the dimensional deviations are initially measured by a suitable measuring device while the drive shaft 1 is rotated around its longitudinal axis B. Depending on the respective dimensional deviations, the drive shaft 1 is permanently deformed slightly by applying a lateral force in such a way as to reduce these deviations. Examples of suitable bend straightening devices were mentioned at the beginning and can be used in this case.

[0053] The force required for bending and straightening depends on the workpiece diameter, wall thickness, material (especially its condition), and the curvature of the component. Forces between 20 kN and 20,000 kN can be required for plastic deformation of the component.

[0054] According to the invention, within the process step of bend straightening (see f in Fig. 1) the rotation of the drive shaft 1 additionally for a rolling action (cf. e in Fig. 1) The welded joints 14a, 14b are used. The drive shaft 1 does not need to be repositioned for this purpose.

[0055] Roller burnishing, according to DIN 8580, is a forming process for surface and edge zone treatment. The components in question are processed with a cylindrical or spherical rolling body, hereinafter also referred to as a roller or ball, made of hard metal or ceramic. The modification of the edge zone is achieved by leveling roughness peaks, introducing compressive residual stresses, and work hardening. The processing load acting on the edge zone during the process can be applied mechanically or hydrostatically. Mechanical load application typically utilizes a spring mechanism, thereby increasing the rolling force F. WThis depends on the stroke of the rolling body. However, a dimensional deviation in the form of out-of-roundness causes a change in the rolling force and thus locally different edge zone properties. In contrast, the load application in hydrostatic roll forming is initiated by a hydrostatic tracking system, which determines the rolling force F. W This is independent of the stroke. This leads to a more uniform effect on the edge zone.

[0056] During roll forming, elastic-plastic deformations are generated in the surface zone, which, depending on the material, tool, and process parameters, act at a distance of 50 µm to 2 mm from the surface. A key objective of roll forming is primarily to smooth the surface. This reduces notch effects in the roughness profile, which has a positive effect on service life.

[0057] Furthermore, when reducing roughness, a distinction can be made between simply leveling the roughness peaks and completely reshaping the surface. Thus, the surface of components made of different materials and with different mechanical properties can be extensively reshaped, provided a sufficient ratio between process-induced load stresses and the yield strength of the component is established.

[0058] Furthermore, roller burnishing allows for the introduction of compressive residual stresses. A suitable ratio of the superposition of the introduced compressive residual stresses with the load stresses resulting from component loading can delay crack initiation and reduce the crack propagation rate, thereby increasing the fatigue strength of the component.

[0059] In addition to the quantitative increase in compressive residual stresses, the characteristics of the residual stress depth profiles, which depend on the hardness of the material being machined, also influence the performance of the components. In soft materials, the residual stress depth profiles are determined by plastic deformation, while in hardened materials they are determined by Hertzian contact stress. The characteristics of the residual stress depth profile can be significantly influenced by adjusting the mechanical load, the rolling element diameter, and the contact area, which, in rotary rolling, relates the feed rate f to the indentation width.

[0060] The required rolling force for the burnishing and / or smoothing process depends on the desired penetration depth and the material and its condition, and can range from more than 0 N up to 2,000 N. The rolling force can be applied via a mechanical, spring-loaded, or hydrostatic system.

[0061] Possible rolling elements include spheres or rollers in the form of cylindrical rollers or conical rolling elements, each of which must have a higher hardness than the material being processed. These rolling elements are classified according to their radii. Suitable radii for hot rolling or burnishing range from 3 mm to 15 mm.

[0062] According to the invention, such roll forming and bend straightening are integrated into the process flow, whereby the individual steps remain functionally independent of one another, i.e., they are not mutually dependent. In other words, it is possible to process individual areas of the drive shaft 1 by roll forming, regardless of whether straightening of the drive shaft is carried out in these areas or at all. Conversely, bend straightening can be carried out in areas where roll forming is not desired.

[0063] According to the invention, both process steps are carried out in the same clamping of the drive shaft 1, thereby saving additional cycle times for reclamping it.

[0064] As already mentioned, the actual straightening process is preceded by a measurement of the drive shaft's straightness. This straightness measurement of drive shaft 1 is a prerequisite for the subsequent bending straightening, as it determines the extent of the required correction.

[0065] According to the invention, the drive shaft 1 is clamped in a bending straightening device after hardening. In this bending straightening device, the drive shaft 1 is also rolled firmly in area A of the weld joint 14a, 14b of the welded sections 10, 11a, 11b.

[0066] In other words, a straightness measurement of the drive shaft 1 for bending straightening and the rolling process are carried out in the same clamping of the drive shaft 1 in the bending straightening device.

[0067] The processes of roll forming and bend straightening can be carried out sequentially. For example, areas A of the welded joints 14a, 14b can first be rolled, followed by straightening and then bend straightening. In principle, the sequence can also be reversed, i.e., straightening and bend straightening can precede roll forming.

[0068] In general, a rotation of the drive shaft 1 around its longitudinal axis B is used both for straightness measurement to detect dimensional deviations in the bending straightening device and for rolling the weld joint to tighten.

[0069] Instead of a strictly sequential process, it is also possible for the straightness measurement to begin during or even before the roll forming process. In this case as well, the bend straightening is performed in the bend straightening device after the roll forming process and after the straightness measurement.

[0070] This enables an almost cycle-time-neutral integration of the hardening rolling process into the forming bending straightening process step within a process for manufacturing multi-part welded drive shafts, such as longitudinal and side shafts of motor vehicles.

[0071] As a further process step, the drive shaft 1 can optionally be started after the rolling and bending rolling.

[0072] The above-described method is particularly suitable for the series production of drive shafts 1 in automotive engineering and, due to its flexibility, also for the rapid and efficient creation and evaluation of prototypes.

[0073] Fig. Figure 2 shows a possible implementation of a bending straightening device 20 with integrated tools for a rolling action.

[0074] The bending court facility 20 according to Fig. 2 initially comprises at least one abutment 21 against which a drive shaft 1, or more generally a shaft, can be supported laterally and rotatably about its longitudinal axis B. In the illustrated embodiment, two abutments 21 are provided by way of example.

[0075] Furthermore, a drive device 22 is provided for rotating the shaft 1 about its longitudinal axis B, which in the embodiment according to Fig. 2 is realized by means of a mandrel clamping. A drive torque is introduced into the shaft 1 via this mandrel clamping of the shaft 1 axially between two mandrels.

[0076] Furthermore, the bending straightening device includes means 23 for measuring the straightness of the shaft 1, with which dimensional deviations, for example due to hardening distortion or the like, can be detected when rotating the shaft 1 about its longitudinal axis B.

[0077] Furthermore, the bending device is equipped with 20 means 24 for straightening the shaft. These can, for example, be applied laterally with a force F. B Pressing against the shaft 1, which is supported against the at least one abutment 20. In this example, only one plunger or ram is shown, which is pressed laterally against the shaft 1 at its midpoint. However, several such means 24 can also be provided and arranged distributed along the length of the shaft 1.

[0078] Furthermore, the bending straightening device includes a roller or roller 25 as a tool for the tightening process, which is arranged opposite the respective abutment 21.

[0079] Furthermore, a pressure device 26 is provided, which is suitable for applying a rolling force F to the roller or cylinder 25. W to push in the direction of the corresponding abutment 21, so that the roller or roll 25 can be brought into lateral contact against the shaft 1 for rolling.

[0080] Suitable feed means enable the roller or cylinder 25 to be moved longitudinally to the shaft 1, so that a section of the desired axial length can be machined by roller burnishing. Furthermore, means can be provided to move the roller or cylinder 25 radially away from and towards the shaft 1 in order to engage and disengage the roller burnishing tool with it.

[0081] When bending and straightening preferably rotationally symmetrical shafts, the shaft 1 is placed on the abutments 21. These are positioned in the area of ​​the welded joints 14a, 14b and can be arranged to be slidably within the bending and straightening device.

[0082] The shaft 1 is then rotated. During the rotation, the straightness of the shaft 1 is measured, for example, using a sensor.

[0083] For straightening, shaft 1 with the greatest deviation is aligned upwards and plastically deformed using a punch or similar tool, essentially bending it slightly in the opposite direction of the deviation. Afterward, shaft 1 is straighter than before the process.

[0084] In the bending straightening device 20, a roll forming process is also carried out in the area of ​​the welded joints 14a, 14b. For this purpose, shaft 1 remains supported at the abutments 21. During rotation and straightness measurement, the roll forming process is performed in the area of ​​the weld seam. This results in plastic deformations and work hardening outside the measuring area even during the measurement.

[0085] Then the rolling force F W Withdrawn. The rollers or rollers 25 move away from the shaft 1 and the actual bending process starts.

[0086] In this combined process of bending straightening and roll forming on multi-part welded shafts 1, both processes are locally separated and do not interact effectively as they do, for example, in straightening roll forming. Rather, both processes run parallel to each other in a single setup, but largely without interaction.

[0087] The rotation of the process is used to determine the feed rate f during the roll forming process as well as the straightness measurement during the bending and straightening process. After the defined areas have been completely hardened by roll forming, the rolling tools move away from the component and the forming and straightening process begins, preferably in the center of the central section 10 of the drive shaft 1 in this example.

[0088] The rolling of both areas A of the welded joints 14a, 14b can be carried out simultaneously, especially since the effective area is practically identical in the example shown. The abutments 21 serve to support the respective counterforce during rolling and straightening.

[0089] The feed rate f is defined here as the relative movement between the drive shaft 1 and the rolling bodies during roll forming in the direction of the longitudinal axis B of the drive shaft 1. The degree of overlap during roll forming with rotary kinematics relates the feed rate f to the indentation width of the rolling body and determines the resulting surface topography and the number of revolutions of the process. Overlap rates from -100% to +100%, preferably -50% to +50%, can be used. Negative overlap rates mean that successive turns of the generated rotating roll paths are axially spaced apart.

[0090] Unlike conventional mechanical processes, the rotational speed not only determines the influence on the surface zone – taking into account feed rate f and rolling speed – but is also crucial for the measurement accuracy of tactile measurements for straightening. Depending on the component size, rotational speeds from more than 0 rpm up to 5,000 rpm can be used.

[0091] Fig. Figure 3 shows another embodiment of a bending straightening device 20', which differs from the bending straightening device 20 according to Fig. 3 differs at least by the tool for rolling and the rotary drive.

[0092] In Fig. 3 A tool 27 with 360° arranged rolling elements around the circumference of the shaft 1 performs the rolling process including the bearing of the shaft 1.

[0093] The rotation of shaft 1 can, for example, be achieved via a clamping device 28 analogous to a chuck of a machine tool. How Fig. As shown by example in Figure 3, the shaft 1 can be clamped at only one end on the clamping device 28 for this purpose.

[0094] For straightening bends, devices analogous to means 22, 23 and 24 can be used according to Fig. 2, however, other devices such as those explained at the beginning may also be used, as long as the shaft 1 is not repositioned between rolling and bending.

[0095] The exemplary embodiments described above enable the efficient integration of measures to increase the strength of multi-part welded drive shafts by avoiding increased cycle times and additional process stations.

[0096] Among other things, it enables simultaneous bend straightening during roll forming at different operational areas in a bend straightening device. Reference symbol list 1 Drive shaft (shaft) 10 central section 11a Final section 11b Final section 12a Coupling structure 12b Coupling structure 13a Hollow shaft section 13b Hollow shaft section 14a Welded joint 14b Welded joint 15 weld bead 20 Biking Court Equipment 20' Bending Court Device 21 abutments 22 Drive unit 23 means for measuring straightness 24 ways to straighten 25 Roller or Roll 26 Pressure device 27 Fixed rolling tool 28 clamping devices A area around the weld joint B Longitudinal axis of the drive shaft (shaft), corresponds to the axis of rotation F B Bending force F W Rolling force f feed

Claims

Method for manufacturing a drive shaft (1) which has at least two sections (10, 11a, 11b) welded together in a material-bonded manner, at least one of which is designed as a hollow shaft, in which a roll forming process is carried out in the area of ​​the welded joint (14a, 14b) of the welded sections, characterized in that the roll forming process is carried out in a bending straightening device (20, 20'), wherein a straightness measurement of the drive shaft (1) for bending straightening and the roll forming process are carried out in the same setup in the bending straightening device (20, 20'). Method according to claim 1, characterized in that a rotation of the drive shaft (1) is used for straightness measurement to detect dimensional deviations in the bending straightening device (20, 20') for the rolling of the weld joint (14a, 14b). Method according to claim 1 or 2, characterized in that the straightness measurement is started during the rolling process. Method according to one of claims 1 to 3, characterized in that bend straightening is carried out in the bend straightening device (20, 20') after the roll forming and after the straightness measurement in the clamping setup for the roll forming. Method according to one of claims 1 to 4, characterized in that the drive shaft (1) is hardened before rolling and / or tempered after rolling. Method according to one of claims 1 to 5, characterized in that a weld bead (15) of the weld joint (14a, 14b) is removed by machining before roll forming. Method according to one of claims 1 to 6, characterized in that the drive shaft (1) in the bending straightening device (20) is rotatably supported on a lateral abutment (21) for bending straightening and a roller or ball (25) for firm rolling is arranged opposite the abutment (21) and is pressed laterally against the drive shaft (1) in the direction of the abutment (21) during firm rolling. Method according to one of claims 1 to 6, characterized in that a fixed rolling tool (27) is provided which surrounds the drive shaft (1) in a ring shape and which also rotatably supports the drive shaft (1). Method according to one of claims 1 to 7, characterized in that the drive shaft (1) has a central section (10) in the form of a hollow shaft and end sections (11a, 11b) connected to its ends, each of which has coupling structures (12a, 12b) for torque transmission. Bending straightening device (20, 20'), comprising at least one abutment (21) against which a shaft (1) can be supported laterally and rotatably about its longitudinal axis (B), a drive device (22) for rotating the shaft (1) about its longitudinal axis (B), means (23) for measuring the straightness of the shaft (1), means (24) for straightening the shaft (1) while it is supported on the at least one abutment (21), characterized by means for roll forming, which are locally separated from the means (24) for straightening, such that bending straightening can be carried out independently of roll forming, wherein the means for roll forming comprise a roller (25) which is arranged opposite the abutment (21), a pressure device (26) which is suitable for pressing the roller (25) towards the abutment (21) so that the roller (25) is in lateral contact with it for roll forming the wave (1) can be brought,and feed means to enable displacement of the roller or cylinder (25) along the shaft (1). Drive shaft (1) for a motor vehicle with at least two sections (10, 11a, 11b) welded together, at least one of which is designed as a hollow shaft, wherein the drive shaft (1) is hardened at a weld joint (14a, 14b) between two of the sections (10, 11a, 11b) welded together and has a machined surface, characterized in that the drive shaft (1) of the weld joint (14a, 14b) between said two sections (10, 11a, 11b) welded together is tempered and has a hot-rolled surface structure with imprinted compressive residual stresses in a radially outer edge region.

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